Means for producing oscillations



Feb. 23 1926., 1,573,948

V D. M. TERRY MEANS FOR PRODUCING OSCILLATIONS Filed NOV. 21, 1923 mmaFeb. 23, 1926.

UNITED STATES PATENT OFF ICE.

' DONALD E. TERRY, OF BROOKLYN, NEW YORK, ASSIGNOR TO- WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MEANS FOR PRODUCING OSCILLATIONSL Application filed November 21, 1923.Serial no. 676,037.

To all whom it may concern:

Be it known that I, DONALD M. Tamar, a

citizen of the United States of America, residing at Brooklyn, in thecounty of Kings and State of New York, have invented certain new anduseful Improvements in Means for Producing Oscillations, of which thefollowing is a full, clear, concise, and exact description. Thisinvention relates to an arrangement for the production of oscillations,and more particularly to an arrangement lnclu ding a three-electrodedischarge device having its input and output circuits coupled infeedback relation to constitute an oscillator which is not sensitive toimpedance changes in the circuits associated with the output terminalsof the oscillator. As is well known, electric discharge osc llators aresensitive to impedance changes 1n the circuits associated with theiroutput terminals. If the impedance of the load C11- cuit coupled to anoscillator is varied, or the coupling means for supplying oscillationsto the load circuit is adjusted, both the frequency and the amplitude ofthe oscillations will b changed. This is due to the fact that theimpedance changes react upon the frequency determining circuit of theoscillator. To overcome this disadvantage, it has heretofore beenproposed to include a reaction preventing device, i. e., either a largeresistance or an asymmetrically conducting repeater between the loadcircuit and the output terminals of the oscillator, whereby im edancechanges are prevented from reacting upon the oscillator.

The present invention contemplates an arrangement in which the circuitsassociated 40 with the oscillating discharge device include means forpreventing impedance changes in the load circuit coupled to theoscillator from reacting thereupon, whether these impedance changes aredue to inherent conditions in the load circuit itself, or to theadjustment of the coupling means for apply-. ingoscillations to the loadcircuit.

In accordance with the present invention an electric discharge devicehas its input and output circuits coupled in feed back control elementis at all times negatively -relation to constitute an oscillator. The

output circuit includes two oscillating current conducting paths. Oneoutput circuit includes a high feed back resistance, for limiting theoperation of the device to the 5 linear portion of its characteristiccurve representing the relation of input voltage to output current,connected in series with a frequency determining circuit. The otheroutput branch includes a resistance connected in series with a means forcoupling the oscillator to a load circuit. The function of theresistance includedin the second output path is to stabilize theoperation of the oscillator.

The input circuit of the oscillator includes a polarizing source whichis adapted to impress a potential upon the control element of thedischarge device of such a value that the polarized relatively to thecathode of the device.

By properly selecting the values of the resistances included in the twobranches of the output circuit of the discharge device relatively to thephysical characteristics of the device and to each other and impressinga polarizing potential of suitable value on the grid of the device, anoscillator is provided which is adapted to generate an oscillatingcurrent of pure wave form and constant frequency, even though theimpedances of the load circuit vary, and the coupling means is adjustedto change the amplitude of the current supplied to the load circuit.

The primary object of the present invention is to produce an oscillatorwhich is not sensitive to impedance changes in the load circuitassociated with it.

Another object is to produce an oscillator, including a dischargedevice, adapted to supply constant frequency oscillations the amplitudeof which may be varied within relatively wide limits.

A further object is an oscillating system comprising a discharge deviceand associated circuits, adapted to produce oscillations of constantfrequency, including means which permits the amplitude of theoscillations supplied by the system to a load circuit to 100 be variedover a wide 'range without changing their frequency.

For a complete understanding of the invention, reference may be made tothe following specification read in conjunction with the attacheddrawing, in which Fig. 1 illustrates an oscillator embodying theinvention and Fig. 2 shows an arrangement similar to that illustrated inFig. 1 including a different coupling means for transferring theoscillating current to a load circuit.

Referring to Fig. 1, there is shown an electric discharge devicecomprising a vessel 1 enclosing a cathode 2, an anode 3, and a controlelectrode or grid 4. Heating current is supplied to the cathode 2 by thesource 5. A source 6, having its negative terminal connected to thecathode 2 and its positive terminal connected to the anode 3 through achoke coil 7, supplies space current to the discharge device. Thecontrol electrode of the grid 4 is negatively polarized by a source 8included in the circuit connecting the cathode and grid of the dischargedevice, which also includes a coupling coil 9.

In addition to the space current path, the output circuit of the deviceis provided with two oscillating current paths. The first path extendsfrom the anode 3 through the blocle ing condenser 10, the resistance 11,tuned circuit 12 to the cathode 2. The circuit 12 serves to determinethe frequency of the oscillations generated. The constants of cirsuit 12may be varied by adjusting either the inductance or capacity, asindicated by the arrows, or by adjusting both of these elements. Theinductance coil included in the tuned circuit 12 is inductivelyassociated with the coil 9, whereby energy is fed back to the inputcircuit.

The second oscillating current output path may be traced from the anode3 through the blocking condenser 10, resistance 13, potentiometer 14,cathode 2 and across the space within the device to the anode 4.

By varying the position of the adjustable contact 15 associated with theresistance 14, the potential impressed upon the input circuits of therepeating device 16, and hence the amplitude of the currents applied tothe circuit 19, may be regulated.

The arrangement illustrated in Fig. 2 is similar to that describedabove. An electric discharge device 1 is provided with an input circuitconnecting its cathode 2 and control electrode 4. The input circuitincludes the polarizing source 8 and coupling coil 9. The outputcircuit, in addition to the space current path including source 6 andchoke coil 7, is provided with two branches through which oscillatingcurrent flows. One oscillating current branch, ex tending from thecathode 2 to the anode 3, includes blocking condenser 10, feed backresistance 11, and frequency determining circuit 12. The inductance coilof the frequency determining circuit is inductively associated with thecoil 9 included in the outputv circuit. By meansof this couplingoscillating current of a frequency determined by the constants of thecircuit 12 is fed back to the input circuit to control the production ofoscillations. The other oscillating currents branch includes aresistance 13 and the primary winding of the repeating coil ortransformer 22, which serves to connect the oscillator to a load circuit23.

In order to produce oscillating current of sinusoidal wave form of thefrequency determined by the constant of the circuit 12, the resistance11 should be sufficiently large to limit the amplitude of the generatedwaves to such a value that the device operates on the most nearly linearportion of its charac teristiocurve representing the relation betweeninput voltage and output current. Again, the inductance coil included inthe frequency determining circuit 12 should be so designed that theratio of its inductance to its resistance should be large and thecoefiicient of coupling between this coil and the coil 9 should also belarge.

The negative potential normally impressed upon the grid of the dischargedevice should be of such value that under all operating conchtions thegrid of the oscillating-device is never permitted to become positiverelatively to its cathode.

With a circuit designed to meet the conditions outlined above and havingthe impedances of the two branches of the output circuit associated withthe device properly proportioned, it has been found that the operationof the oscillator is so stable that the amplitude of the oscillationssupplied to the load circuit through the'potentiometer or couplingtransformer may be varied over a wide range without causing anappreciable change in the frequency of the oscillations produced by theoscillator. Hence, by choosing the resistance 13 included in the loadcoupling branch of the output circuit, vsuch that the impedance of thisbranch bears a definite relation to the impedance of the feed backbranch, including the resistance 11 and the frequency determiningcircuit 12, it is possible to provide an oscillator adapted to supplyoscillations of constant frequency and adjustable amplitude to a loadclrcui r Experiments have been made with an oscillator of the designdescribed above adapted to produce oscillations of 8330 cycles, whichincludes an electric discharge device having physical characteristicssuch that when a heating current of 1.3 ampcres is supplied to itscathode, a potential of 120 volts is impressed upon its plate electrode,and a polarizing potential of 4.5 volts is impressed upon its grid, theinternal plate order of 6000 ohms.

circuit impedance of the device is of the ance of 230,000 ohms was used,the time constant of the coil included in the frequency determiningcircuit as identified by the fraction (where w=21r{, L=inductance andRr= rcsistance) was 77, the coefficient of coupling was about .95 andthe load coupling branch included a resistance of 96,000 ohms and apotentiometer of 16,000 ohms.

When the filament heating current was changed from 1.2 to 1.4 amperes,the frequency of the oscillations produced varied .021 per cent.Changing the plate voltage from 100 to,140 volts caused the frequency ofthe oscillations to vary .012 per cent, and when the potentiometer wasadjusted over its complete range, whereby the amplitude of theoscillations supplied to the load circuit was varied from zero to 10milliamperes, it was impossible to detect any change in the frequency ofthe oscillations generated.

It will therefore be seen that this-invention provides an oscillator,comprising a single electric discharge device and its associatedcircuits, which, while permitting the value of the oscillating energyavailable at its output terminals for transmission to a load circuit tobe adjusted over a wide range, is as stable or even more stable thanelectric discharge oscillators hitherto proposed.

Thus, in the arrangement described above the output terminals of theoscillator may be directly associated with a load circuit and greatflexibility is permitted in adjusting the value of the oscillatingenergy supplied to a load circuit without introducing disturbingreactions into the oscillator circuits.

While in the preceding description specific arrangements and detailshave been set forth for the purpose of completely disclosing the natureof the present invention, it is to be understood that this invention isnot limited to the details of the circuits and apparatus disclosed, butonly by the scope of the attached claims.

What is claimed is:

1. An oscillation generator comprising an electric discharge devicehaving a cathode, an anode and a grid, input and output circuitsconnected in feed back relation to generate oscillations of constantfrequency, said output circuit having a plurality of oscillating currentpaths, one of said paths con stituting a feed back path coupled to saidinput circuit, means included in each of the oscillating current pathsof said circuits for stabilizing the operation of the oscillator, andadjustable coupling means for varying the value of the constantfrequency oscillat- 'A' feed back resisting energy available at theoutput termin'als of the oscillator for transmission to a load circuit.

2. An oscillation generator comprising an electric discharge devicehaving a cathode, an anode and a grid, input and output circuitsconnected in feed back relation to produce oscillations of constantfrequency, means for maintainin the grid of said device at all timesnegatively polarized relatively to its cathode, an output oscillatingcurrent branch including a frequenc determining circuit and astabilizing impe ance, a second output oscillating current branchincluding stabilizing means and adjustable means for coupling theoscillator to a load circuit,

whereby the constant frequency oscillating energy available fortransmission to a load circuit may be varied.

3. An oscillation generator comprising an electric discharge devicehaving a cathode, an anode and a control electrode, and input and outputcircuits therefor, the output circuit including two parallel connectedbranches, one of which includes a high resistance and is coupled to theinput circuit to control theproduction of oscillations, and the otherbranch includes a stabilizing resistance and also means for coupling theoscillator to a load circuit.

4. An oscillation enerator comprising an electric discharge devicehaving a cathode, an anode and a control electrode, input and outputcircuits therefor coupled in feed back relation, a feed back pathincluding a frequency determining circuit and a resistance in seriestherewith, a second oscillating current path connected in parallel withthe feed back path and including coupling means for a load circuit and astabilizing resistance.

5. An oscillation generator comprising an electric discharge devicehaving a cathode, an anode and a control electrode, input and outputcircuits therefor coupled in feed back relation, said input circuitincluding a source for maintaining the control electrode at all timesnegatively polarized relatively to said cathode, a feed back pathincluding a -fre quency determining circuit and a resistance in seriestherewith, a-second oscillating cur rent path connected in parallel withthe feed back path and including coupling means for a load circuit and astabilizing resistance.

.6. An oscillation generator comprising an electric discharge devicehaving a cathode, an anode and a control electrode, input and outputcircuits therefor coupled in feed back relation, a feed back pathincluding a frequency determining circuit and a resistance, a secondoscillating current path including coupling means for a load circuit anda resistance, the ratio of the impedance of the feed back path to thatof the load circuit coupling path being substantially fixed.

IEO

7. A space discharge oscillator comprising a grid circuit containing acoupling coil, an anode-cathode ath containing a direct current sourceand an inductance of high value, another anode-cathode path containing acondenser, a resistance and a tuned loop in series, the inductance ofsaid loop being coupled to said grid circuit coil, a coupling path fromthe junction oint of 10 said condenser and resistance to sa1d cathode,said coupling path including large ohmic resistance, and a load circuitcou led to other impedance means in said coup ing pat 8. A combinationin accordance with claim 15 7 in which said other impedance means is aresistance of relatively small value.

In witness whereof, hereunto subscribe ngsname this 14th day ofNovember, A. D. 1

DONALD M. TERRY,

